1. Technical Field
The present invention relates in general to flexible cables used in disk drives and, in particular, to an improved system, method, and apparatus for an independent flexible cable damper for reducing flexible cable fatigue in hard disk drives.
2. Description of the Related Art
Magnetic disk drives are information storage devices that utilize at least one rotatable magnetic media disk having concentric data tracks defined for storing data. A magnetic recording head or transducer reads data from and/or writes data to the various data tracks. A slider supports the transducer in proximity to the data tracks typically in a flying mode above the storage media. A suspension assembly resiliently supports the slider and the transducer over the data tracks. A positioning actuator is coupled to the transducer/slider/suspension combination for moving the transducer across the media to the desired data track and maintaining the transducer over the data track center line during a read or a write operation.
The transducer is attached to or is formed integrally with the slider which supports the transducer above the data surface of the storage disk by a cushion of air, referred to as an air-bearing, generated by the rotating disk. Alternatively, the transducer may operate in contact with the surface of the disk. Thus, the suspension provides desired slider loading and dimensional stability between the slider and an actuator arm which couples the transducer/slider/suspension assembly to the actuator.
The actuator positions the transducer over the correct track according to the data desired on a read operation or to the correct track for placement of the data during a write operation. The actuator is controlled to position the transducer over the desired data track by shifting the combination assembly across the surface of the disk in a direction generally transverse to the data tracks.
The actuator may include a single arm extending from a pivot point, or alternatively a plurality of arms arranged in a comb-like fashion extending from a pivot point. A rotary voice coil motor (vcm) is attached to the rear portion of the actuator arm or arms to power movement of the actuator over the disks. The term seek refers generally to the radial movement of the heads or transducer to a specified track on the disk.
The vcm located at the rear portion of the actuator arm is comprised of a top plate spaced above a bottom plate with a magnet or pair of magnets therebetween. The vcm further includes an electrically conductive coil disposed within the rearward extension of the actuator arm and between the top and bottom plates, while overlying the magnet in a plane parallel to the magnet. In operation, current passes through the coil and interacts with the magnetic field of the magnet so as to rotate the actuator arm around its pivot and thus positioning the transducer as desired.
The magnetic media disk or disks in the disk drive are mounted to a spindle. The spindle is attached to a spindle motor which rotates the spindle and the disks to provide read/write access to the various portions on the concentric tracks on the disks. One or more electrical conductors extend over the suspension assembly to electrically connect the read/write transducer to a read/write chip on the actuator arm.
A multiline flexible printed circuit cable (actuator flexible cable) provides the electrical contact between the read/write chip and the disk drive electronics which are mounted outside the disk drive housing. Inside the disk drive housing, the actuator flexible cable connects to an electrical connector pin assembly, which in turn, through an opening or connector port in the housing, connects to the external electronics.
The actuator flexible cable is a flexible circuit that carries electrical signals to and from the actuator. It is typically comprised of a plurality of electrical conductors encapsulated within an insulating material, for example polyimide. The actuator flexible cable provides electrical contact from the external electronics fixed to the disk drive housing to the actuator which is supported on bearings allowing radial motion of the actuator about its pivot point. The radial motion of the actuator allows the read/write transducers supported on suspensions fixed to the actuator to access data tracks on the disk surfaces located at any radial position from the disk ID to the disk OD.
The preferred method of fixing the actuator flexible cable between electronics card on the fixed disk drive housing and the rotatable actuator is to form the actuator flexible cable in a loop so that the actuator flexible cable causes minimal constraint on the actuator rotation. The loop of actuator flexible cable connecting the actuator with the electronics card can vibrate during seeking of the actuator, introducing unwanted vibration modes to the actuator. Flexible cable induced vibration, also known as random transient vibration or RTV, of the actuator during seek operations degrades settling performance of the disk drive.
There have been attempts in the prior art to minimize the affects of the flexible cable on the actuator or head carriage assembly. For example, one solution uses a double-sided pressure sensitive adhesive tape between the flexible cable and the actuator arm to mitigate deformation of the head carriage. Another solution uses a reducing member supporting mechanism and a reducing member sandwiched together at the base plate where the flexible cable attaches to the disk drive housing.
FIG. 1 depicts another conventional solution to overcoming RTV in actuators. A patched damper 11 is attached directly to a surface of a flexible cable 13 near the actuator. Patched dampers are critical but vulnerable components that can break during the actuator's seeking motion due to stress concentrations and fatigue. Thus, although these designs are workable, an improved solution that provides the necessary RTV attenuation but overcomes the limitations of the prior art would be desirable.